Prior approaches to entering fractions into a calculator have relied upon the pressing of keys in predetermined patterns to indicate a characteristic or whole number part, a numerator, and a denominator. See, for example, the techniques described and shown in U.S. Pat. Nos. 5,089,980 to Bunsen et al. and 5,025,403 to Stephens and Japanese Patent Application No. 50-115061. Although these techniques work well for allowing a user to select different numerators and denominators, they require a relatively large number of keystrokes to enter a fraction into a calculator. Consequently the chance for error is greater and the user must proceed slower and more cautiously than he might otherwise desire.
In some circumstances, a user may wish to enter some data that share a first common denominator and other data that share a second common denominator. For example, the user may need to enter some measurements in thirds and other measurements in fourths. Using the prior techniques described above requires the user to repeat the same keystroke patterns over and over again. Yet utilizing a dedicated fraction key such as disclosed in U.S. Pat. No. 4,081,859 is not a solution. Dedicated fraction keys are limited to entering only predefined fractions. Given the limited area on the keyboard of a calculator, only a few of such keys may be supplied.
The invention overcomes the drawbacks of these prior techniques by allowing a user to store any denominator value as a default value and then select it for use in a fraction with only a single keystroke.